1. Field of the Invention
The present invention relates generally to dry powder compositions and methods for their preparation and use. In particular, the present invention relates to methods for spray drying pharmaceutical and other compositions comprising a hydrophobic drug or other component and a hydrophilic excipient or other component.
Over the years, certain drugs have been sold in formulations suitable for oral inhalation (pulmonary delivery) to treat various conditions in humans. Such pulmonary drug delivery formulations are designed to be inhaled by the patient so that the active drug within the dispersion reaches the lung. It has been found that certain drugs delivered to the lung are readily absorbed through the alveolar region directly into blood circulation. Such pulmonary delivery can be effective both for systemic delivery and for localized delivery to treat diseases of the lungs.
Pulmonary drug delivery can itself be achieved by different approaches, including liquid nebulizers, aerosol-based metered dose inhalers (MDI""s), and dry powder dispersion devices. Aerosol-based MDI""s are losing favor because they rely on the use of chlorofluorocarbons (CFC""s), which are being banned because of their adverse effect on the ozone layer. Dry powder dispersion devices, which do not rely on CFC aerosol technology, are promising for delivering drugs that may be readily formulated as dry powders.
The ability to deliver pharmaceutical compositions as dry powders, however, is problematic in certain respects. The dosage of many pharmaceutical compositions is often critical, so it is desirable that dry powder delivery systems be able to accurately, precisely, and reliably deliver the intended amount of drug. Moreover, many pharmaceutical compositions are quite expensive. Thus, the ability to efficiently formulate, process, package, and deliver the dry powders with a minimal loss of drug is critical. With dry powder drug delivery, both the delivered dose efficiency, i.e. the percentage of drug from a unit dose receptacle which is aerosolized and delivered from a delivery device, and the median particle size distribution, i.e. the deviation from the median size, are critical to the successful delivery of powders to a patient""s lungs.
A particularly promising approach for the pulmonary delivery of dry powder drugs utilizes a hand-held device with a hand pump for providing a source of pressurized gas. The pressurized gas is abruptly released through a powder dispersion device, such as a venturi nozzle, and the dispersed powder made available for patient inhalation. While advantageous in many respects, such hand-held devices are problematic in a number of other respects. The particles being delivered are usually less than 5 xcexcm in size, making powder handling and dispersion more difficult than with larger particles. The problems are exacerbated by the relatively small volumes of pressurized gas, which are available using hand-actuated pumps. In particular, venturi dispersion devices are unsuitable for difficult-to-disperse powders when only small volumes of pressurized gas are available with the handpump. Another requirement for hand-held and other powder delivery devices is efficiency. High device efficiency in delivering the drug to the patient with the optimal size distribution for pulmonary delivery is essential for a commercially viable product.
Spray drying is a conventional chemical processing unit operation used to produce dry particulate solids from a variety of liquid and slurry starting materials. The use of spray drying for the formulation of dry powder pharmaceuticals is known, but has usually been limited to spray drying of hydrophilic drugs in aqueous solutions, usually in combination with hydrophilic excipients. Many drugs, however, are hydrophobic, preventing spray drying in aqueous solutions. While spray drying of hydrophobic materials can often be accomplished using an organic solvent, the use of such non-aqueous solvents generally limits the ability to simultaneously spray dry a hydrophilic excipient.
For these reasons, it would be desirable to provide improved methods for spray drying pharmaceutical and other compositions which comprise both hydrophobic and hydrophilic components, such as hydrophobic drugs and hydrophilic excipients. Such spray drying methods should be compatible with a wide variety of hydrophobic drugs as well as conventional hydrophilic excipients, such as povidone (polyvinylpyrrolidone) and other water soluble polymers, citric acid, mannitol, pectin and other water soluble carbohydrates, and particularly with those excipients which are accepted for use in inhalation formulations, such as lactose, sodium chloride, and sodium citrate. Such spray drying methods will preferably produce particles having a uniform size distribution, with a mean particle size below 10 xcexcm, preferably below 5 xcexcm, and a standard deviation less than or equal to xc2x12 xcexcm. Such powders should further exhibit uniform composition from batch to batch so that any tendency for particles of different compositions and/or sizes to separate in the lungs will have a reproducible impact on the therapeutic effect. Additionally, such spray drying methods should provide for dry powders which are physically and chemically stable and which have low levels of any residual organic solvents or other components which might be used in the spray drying process. At least some of the above objectives will be met by the various embodiments of the present invention which are described in detail below.
2. Description of the Background Art
Methods for spray drying hydrophobic and other drugs and components are described in U.S. Pat. Nos. 5,000,888; 5,026,550; 4,670,419, 4,540,602; and 4,486,435. Bloch and Speison (1983) Pharm. Acta Helv 58:14-22 teaches spray drying of hydrochlorothiazide and chlorthalidone (lipophilic drugs) and a hydrophilic adjuvant (pentaerythritol) in azeotropic solvents of dioxane-water and 2-ethoxyethanol-water. A number of Japanese Patent application Abstracts relate to spray drying of hydrophilic-hydrophobic product combinations, including JP 806766; JP 7242568; JP 7101884; JP 7101883; JP 71018982; JP 7101881; and JP 4036233. Other foreign patent publications relevant to spray drying hydrophilic-hydrophobic product combinations include FR 2594693; DE 2209477; and WO 88/07870.
WO 96/09814 describes spray dried pharmaceutical powders. In particular, Example 7 describes spray drying budesonide and lactose in ethanol where the budesonide is partially soluble and the lactose is insoluble. U.S. Pat. Nos. 5,260,306; 4,590,206; GB 2 105 189; and EP 072 046 describe a method for spray drying nedocromil sodium to form small particles preferably in the range from 2 to 15 xcexcm for pulmonary delivery. U.S. Pat. No. 5,376,386, describes the preparation of particulate polysaccharide carriers for pulmonary drug delivery, where the carriers comprise particles sized from 5 to 1000 xcexcm. Mumenthaler et al. (1994) Pharm. Res. 11:12 describes recombinant human growth hormone and recombinant tissue-type plasminogen activator. WO 95/23613 describes preparing an inhalation powder of DNase by spray drying using laboratory-scale equipment. WO 91/16882 describes a method for spray drying proteins and other drugs in liposome carriers.
The following applications assigned to the assignee of the present application each describe that spray drying may be used to prepare dry powders of biological macromolecules; application Ser. No. 08/644,681, filed on May 8, 1996, which was a continuation-in-part of application Ser. No. 08/423,515, filed on Apr. 14, 1995; application Ser. No. 08/383,475, which was a continuation-in-part of application Ser. No. 08/207,472, filed on Mar. 7, 1994; application Ser. No. 08/472,563, filed on Apr. 14, 1995, which was a continuation-in-part of application serial no. 08/417,507, filed on Apr. 4, 1995, now abandoned, which was a continuation of application Ser. No. 08/044,358, filed on Apr. 7, 1993, now abandoned; application Ser. No. 08/232,849, filed on Apr. 25, 1994, which was a continuation of application Ser. No. 07/953,397, now abandoned. WO 94/07514 claims priority from Ser. No. 07/953,397. WO 95/24183 claims priority from Ser. Nos. 08/207,472 and 08/383,475.
According to the present invention, methods for spray drying hydrophobic drugs and other materials are provided which overcome at least some of the deficiencies noted above with respect to prior spray drying processes. In particular, the spray drying methods of the present invention permit the simultaneous spray drying of the hydrophobic component with a hydrophilic component, such as a hydrophilic pharmaceutical excipient, under conditions which result in a dry powder comprising mixtures of both the hydrophilic and hydrophobic components. Although the methods of the present invention are particularly useful for forming pharmaceutical compositions where the hydrophobic component is a hydrophobic drug, usually present at from 0.01% to 95% of the powder, and the hydrophilic component is a hydrophilic excipient, usually present at from 99.99% to 5% of the powder, the methods may be applied more broadly to form dry powders comprising a variety of hydrophobic and hydrophilic components at different concentration ranges, including hydrophilic drugs and hydrophobic excipients.
The spray drying methods of the present invention are compatible with at least most hydrophilic pharmaceutical excipients, particularly including mannitol, povidone, pectin, lactose, sodium chloride, and sodium citrate. Use of the latter three excipients is particularly preferred for powders intended for pulmonary delivery as they are xe2x80x9cgenerally recognized as safexe2x80x9d(GRAS) for such applications. The methods are also suitable for use with numerous hydrophobic drugs and nutrients, including steroids and their salts, such as budesonide, testosterone, progesterone, estrogen, flunisolide, triamcinolone, beclomethasone, betamethasone; dexamethasone, fluticasone, methylprednisolone, prednisone, hydrocortisone, and the like; peptides, such as cyclosporin and other water insoluble peptides; retinoids, such as all-cis retinoic acid, 13-trans retinoic acid, and other vitamin A and beta carotene derivatives; vitamins D, E, and K and water insoluble precursors and derivatives thereof; prostaglandins and leukotrienes and their activators and inhibitors including prostacyclin (epoprostanol), and prostaglandins E1 E2; tetrahydrocannabinol; lung surfactant lipids; lipid soluble antioxidants; hydrophobic antibiotics and chemotherapeutic drugs such as amphotericin B adriamycin, and the like.
The spray drying methods can produce a uniform particle size distribution. For example, the mean particle diameter can be controlled below 10 xcexcm, preferably below 5 xcexcm, with a size distribution (standard deviation) less than xc2x12 xcexcm. The particles of the powders so produced have a minimum batch-to-batch variability in composition, and are physically and chemically stable. The powders have minimum residual organic solvents to the extent they may have been used in the spray drying process.
In a first aspect of the method of the present invention, an aqueous solution of the hydrophulic component is prepared, typically by mixing in water under a vacuum or reduced pressure. The hydrophobic component is then suspended in the aqueous solution of the hydrophilic component to form a suspension. The suspension is then spray dried to form particles comprising of both the hydrophilic and the hydrophobic components. Usually, the hydrophobic component will have an aqueous solubility less than 5 mg/ml, more usually below 1 mg/ml. The hydrophilic component will have a concentration in the aqueous solution in the range from 1 mg/ml to 100 mg/ml, usually from 5 mg/ml to 60 mg/ml, and the hydrophobic component is suspended in the solution to a concentration in the range from 0.01 mg/ml to 10 mg/ml, usually from 0.05 mg/ml to 5 mg/ml.
In a second aspect, the method of the present invention comprises preparing a solution of a hydrophobic component in an organic solvent. The hydrophilic component is then suspended in the organic solvent to form a suspension. The suspension is then spray dried to form particles comprising both the hydrophobic and hydrophilic components. Usually, the hydrophobic component has a solubility of at least 0.1 mg/ml, preferably being at least about 1 mg/ml. The hydrophilic component will usually have a solubility below 5 mg/ml in the organic solvent, more usually being below 1 mg/ml. In the organic suspension, the hydrophobic component preferably has a concentration in the range from 0.01 mg/ml to 10 mg/ml, more preferably from 0.05 mg/ml to 5 mg/ml, and the hydrophilic component is usually suspended to a concentration in the range from 1 mg/ml to 100 mg/ml, more usually from 5 mg/ml to 60 mg/ml. Preferred organic solvents include alcohols, ketones, hydrocarbons, and the like.
In a third aspect, the method of the present invention comprises at least partially dissolving hydrophilic component in an organic solvent or cosolvent system. The hydrophobic component is at least partially dissolved in the same organic solvent or cosolvent system to produce a solution. The organic solvent solution or cosolvent system is then spray dried to form particles comprising a mixture of the hydrophilic and hydrophobic components. The organic solvent will be selected to provide a solubility for the hydrophilic component of at least 1 mg/ml, preferably at least 5 mg/ml, and a solubility for the hydrophobic component of at least 0.01 mg/ml, preferably at least 0.05 mg/ml. Usually, the hydrophilic component will have a concentration in the organic solvent or cosolvent system solution from 1 mg/ml to 100 mg/ml, preferably from 5 mg/ml to 60 mg/ml, and the hydrophobic component will have a concentration from 0.01 mg/ml to 10 mg/ml, preferably from 0.05 mg/ml to 5 mg/ml. Suitable organic solvents or solvent systems are selected to provide such minimum solubility characteristics, but it is preferred if the organic solvent or cosolvent system provides solubilities well in excess of the stated minimums.
In a fourth aspect, the method of the present invention comprises preparing an aqueous solution of a hydrophilic component and an organic solution of a hydrophobic component in an organic solvent. The aqueous solution and the organic solution are simultaneously spray dried to form particles comprising a mixture of the hydrophilic and hydrophobic components. Usually the hydrophilic component has a concentration in the aqueous solution from 1 mg/ml to 100 mg/ml, preferably from 5 mg/ml to 60 mg/ml. The hydrophobic component has a solubility in the organic solution of at least 0.01 mg/ml, preferably at least 0.05 mg/ml. The concentration of the hydrophobic component in the organic solution is usually in the range from 0.01 mg/ml to 10 mg/ml, preferably from 0.05 mg/ml to 5 mg/ml. Preferred organic solvents include alcohols, ketones, ethers, aldehydes, hydrocarbons, and polar aprotic solvents, and the like. The use of a separate aqueous and organic solution to carry the hydrophilic and hydrophobic components, respectively, is advantageous in that it allows a much broader range of selection for the organic solvent, since the organic solvent does not also have to solubilize the hydrophilic component. Usually, the aqueous solution and organic solution will be spray dried through a common spray nozzle, more usually through a coaxial spray nozzle.
Powders prepared by any of the above methods will be collected from the spray dryer in a conventional manner for subsequent use. For use as pharmaceuticals and other purposes, it will frequently be desirable to disrupt any agglomerates which may have formed by screening or other conventional techniques. For pharmaceutical uses, the dry powder formulations will usually be measured into a single dose, and the single dose sealed into a package. Such packages are particularly useful for dispersion in dry powder inhalers, as described in detail below. Alternatively, the powders may be packaged in multiple-dose containers.
The present invention further comprises dry powder compositions produced according to the methods described above, as well as unit dose and multidose packages of such dried powder compositions containing a therapeutically effective amount of the dry powder.
The present invention further provides methods for aerosolizing a dry powder composition comprising the steps of providing an amount of dry powder composition produced by any of the methods described above and subsequently dispersing the dry powder composition into a flowing gas stream.